Introduction to Chemistry

Introduction to Chemistry

• Chemistry Definition: Study of matter, its properties, and the changes it undergoes.
• Branches of Chemistry:
  • Organic Chemistry: Study of carbon-containing compounds.
  • Inorganic Chemistry: Study of inorganic compounds.
  • Physical Chemistry: Study of the physical properties and behavior of chemical systems.
  • Analytical Chemistry: Techniques to analyze substances.
  • Biochemistry: Study of chemical processes in living organisms.

Basic Concepts

• Matter: Anything that has mass and occupies space.
• States of Matter:
  • Solid: Definite shape and volume.
  • Liquid: Definite volume, indefinite shape.
  • Gas: Indefinite shape and volume.
• Properties of Matter:
  • Intensive Properties: Independent of the amount (e.g., density, boiling point).
  • Extensive Properties: Dependent on the amount (e.g., mass, volume).

Atomic Structure

• Atom: Basic unit of matter, composed of protons, neutrons, and electrons.
• Subatomic Particles:
  • Protons: Positively charged, in the nucleus.
  • Neutrons: Neutral, in the nucleus.
  • Electrons: Negatively charged, orbiting the nucleus.
• Atomic Number (Z): Number of protons in an atom.
• Mass Number (A): Total number of protons and neutrons.

Periodic Table

• Organization: Elements arranged by increasing atomic number.
• Groups: Vertical columns (similar chemical properties).
• Periods: Horizontal rows (varying properties).
• Key Groups: Alkali metals, alkaline earth metals, transition metals, halogens, noble gases.

Chemical Bonding

• Ionic Bond: Transfer of electrons from one atom to another.
• Covalent Bond: Sharing of electrons between atoms.
• Metallic Bond: Pooling of electrons among a lattice of metal atoms.

Stoichiometry

• Mole Concept: 1 mole = 6.022 x 10²³ particles.
• Molecular Weight: Sum of atomic weights in a molecule.
• Balancing Reactions: Ensuring the number of atoms is the same on both sides of a reaction.

Chemical Reactions

• Types of Reactions:
  • Synthesis: A + B → AB.
  • Decomposition: AB → A + B.
  • Single Replacement: A + BC → AC + B.
  • Double Replacement: AB + CD → AD + CB.
  • Combustion: Hydrocarbon + O₂ → CO₂ + H₂O.

Solutions

• Solvent: Substance in greater amount (usually liquid).
• Solute: Substance dissolved in the solvent.
• Concentration: Amount of solute per unit volume of solution (e.g., molarity).

Acids and Bases

• Acids: Substances that release H⁺ ions in solution (e.g., HCl, sulfuric acid).
• Bases: Substances that accept H⁺ ions or produce OH⁻ ions (e.g., NaOH).
• pH Scale: Measure of acidity/alkalinity (0-14 scale; 7 is neutral).

Thermodynamics

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.
• Endothermic Reactions: Absorb heat (e.g., photosynthesis).
• Exothermic Reactions: Release heat (e.g., combustion).

Conclusion

• Fundamental concepts of chemistry are essential for understanding more complex chemical interactions and reactions encountered in higher studies and practical applications.